Autoimmunity plays a key role in many endocrine diseases including thyrotoxicosis, thyroditis, adrenal insufficiency and Type I diabetes (DM). Changes in T cell subsets, association with HLA antigens, and the presence of autoantibodies strongly support an immunopathological mechanism in the etiology of these disorders. Understanding the immunoregulatory abnormalities is limited by the lack of information on the antigens recognized by these autoantibodies and by the lack of a reliable assay for the antibodies. To address these problems we have developed a cell surface enzyme-linked immunoassay (CELISA) for the detection of organ specific autoantibodies. In this project, we employ anti-islet antibodies as prototypes for the investigation of Type I DM and other endocrinopathies. We show the CELISA detects IgG anti-islet antibodies in the sera of many patients with recent onset Type I DM. Our preliminary data indicate that these antibodies are heterogeneous and are consistent with animal studies that find both glycoproteins and glycolipids to be targets of anti-islet antibodies. In this research we will identify the antigens recognized by anti-islet antibodies from diabetics, and determine if these antigens are glycoproteins or glycolipids. The prevalence of these antigens on other neuro-endocrine tissues and their role in other autoimmune disorders will be ascertained. In addition, studies of the immunochemical characteristics of anti-islet antibodies will be carried out and will include determination of heavy chain isotype, light chain type, and charge heterogeneity. Functional studies will be performed to determine which antibodies have the greatest cytotoxic effect on islet cells. These data will be further combined with the genetic information obtained from HLA studies of families of affected individuals. In the future this information may be used to identify subjects at risk for disease, and will also be valuable in monitoring therapeutic interventions such as immunosuppressive therapy and islet transplantation. In the long term, identification of antigens recognized by T lymphocytes will provide the opportunity for more selective intervention at the cellular level.